JPH1080634A - Catalyst synthesizing liquid phase methanol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst remarkably small in the change of methanol forming rate with time and excellent in stability in a method for producing methanol from a gaseous mixture of hydrogen with a carbon oxide in the presence of a solvent. SOLUTION: This catalyst for synthesizing methanol by allowing the gaseous mixture of hydrogen with the carbon oxide to react with each other in the presence of the solvent is composed of metallic components consisting essentially of copper and zinc, contains further a graphite having <=1wt.% ash (preferably <=0.1wt.%) and the content of the graphite occupied in the whole catalyst is setted to 10-30wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid phase methanol synthesis catalyst for producing methanol from a mixed gas of hydrogen and carbon oxides (carbon dioxide, carbon monoxide) in the presence of a solvent. is there.

[0002]

2. Description of the Related Art At present, methanol is industrially produced by bringing a raw material gas comprising hydrogen and carbon oxide into contact with a copper-zinc oxide catalyst in a gas phase reaction.

[0003] From the viewpoint of removing the heat of reaction, which is a problem of the gas phase process, there have been many studies on the development of the liquid phase process.

The latter liquid phase process is a method in which a liquid solvent having a large heat capacity coexists in a reactor, and the reaction heat is absorbed by the liquid solvent and removed from the system. According to this method,
Since the removal of the heat of reaction is much easier than in the case of the gas phase process, it is expected that the conversion rate of the raw material gas and the methanol yield can be improved, and the production of methanol by the liquid phase process has received considerable attention. ing.

For example, a method under development at Air Products and Chemicals (US Pat. No. 4,031,123)
No.) suspends a copper-zinc oxide catalyst in a water-insoluble solvent, blows a raw material gas from below at 200 to 270 ° C. and 60 atm, and moves generated methanol and unreacted raw material gas upward from the reactor. It is discharged in gaseous form.

[0006] In addition, at the meeting of Catalyst Deactivation 1991, when the catalyst is deteriorated, it is attempted to maintain the amount of methanol produced by extracting a part of the catalyst and replenishing it with a new catalyst.

[0007]

When methanol is synthesized by bringing a raw material gas composed of hydrogen and carbon oxide into contact with a copper-zinc oxide catalyst in a liquid phase reaction, when the above-mentioned suspension bed is used, Although it is possible to replace part of the catalyst while operating to maintain the amount of methanol produced, it is difficult to maintain the methanol production rate at the beginning of the reaction. On the other hand, in the case of a fixed floor, the operation is stopped,
The catalyst needs to be replaced.

[0008] Therefore, it is desired to develop a catalyst having excellent stability with little change over time in the rate of methanol generation in both the suspension bed and the fixed bed.

When methanol is produced from a mixed gas of hydrogen and carbon oxides containing carbon dioxide, water is produced together with methanol, so that by-products are produced in a liquid phase process in which the reaction is carried out in the presence of a solvent. Water has a negative effect on the catalyst.

To reduce this effect, Lee et al.
EL SCIENCE AND TECHNOLOGY INT 'L., 9 (8), 977 (199
1)) states that by pre-treating a copper-zinc oxide-based methanol synthesis catalyst with carbon dioxide, it is possible to turn zinc oxide contained in the catalyst into zinc carbonate and to suppress copper crystal growth. ing. However, this method is also insufficient for obtaining a stable methanol production rate.

Under such a background, the present invention provides a method for producing methanol from a mixed gas of hydrogen and carbon oxide in the presence of a solvent, which is excellent in stability with a very small change in methanol production rate with time. It is an object of the present invention to provide a catalyst.

[0012]

The liquid phase methanol synthesis catalyst of the present invention is a catalyst for synthesizing methanol by reacting a raw material gas comprising hydrogen and carbon oxide in the presence of a solvent. The catalyst comprises a metal component mainly composed of copper and zinc, further contains graphite having an ash content of 1% by weight or less, and the content of the graphite in the whole catalyst is 10%.
-30% by weight.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

<Catalyst Composition> In the present invention, a liquid phase methanol synthesis catalyst which comprises a metal component containing copper and zinc as main components and further contains graphite is used. The point of the present invention is that graphite is contained as described above.

This catalyst may further contain at least one metal component selected from the group consisting of aluminum, zirconium and gallium, in addition to the above-mentioned copper, zinc and graphite.

The metal component in the catalyst is usually copper
u or partially in the form of oxides of Cu, zinc in the form of ZnO and optionally ZnCO ₃ , and aluminum in the form of Al ₂ O
_In the form ( ₃ ), zirconium is present in the form of ZrO ₂ and gallium is present in the form of Ga ₂ O ₃ .

Copper component (copper or copper oxide) in the catalyst
Is suitably 20 to 80% by weight, and the content of the zinc component (zinc compound) is suitably 10 to 70% by weight. The content of other metal components (compounds of aluminum, zirconium and gallium) is suitably from 0 to 60% by weight in total. By appropriately determining the content of these metal components according to the composition of the reaction raw material gas, optimal catalytic performance can be obtained.

In the present invention, the ash content of the graphite coexisting in the catalyst is 1% by weight or less (preferably 0.5% by weight or less, more preferably 0.1% by weight or less).
Use If the ash content exceeds 1% by weight,
Not only does the effect decrease because the amount of pure graphite decreases, but also the active component decreases because SiO _2, which is the main component of the ash component in the graphite, reacts with the metal component that is the active component. It is difficult to suppress the change within an allowable range.

The ash content in graphite can be reduced by using an acid such as hydrochloric acid or hydrofluoric acid. The smaller the ash content, the more advantageous. However, it is difficult to completely remove the ash, and the cost is low. It takes too much. However, as described above, it is relatively easy to reduce the ash content to 1% by weight or less, and if the ash content is 1% by weight or less, the decrease in activity is kept within an allowable range.

The amount of graphite in the whole catalyst is set at 10 to 30% by weight. When the amount of graphite is too small, the effect of preventing the catalyst from deteriorating and the effect of improving the activity cannot be sufficiently obtained, and the change over time in the methanol production rate becomes large. On the other hand, when the amount of graphite is too large, although there is an effect in terms of preventing catalyst deterioration, the proportion of components other than graphite is relatively small, so that the amount charged into the reactor is substantially reduced accordingly. And as a result, the productivity of methanol decreases.

<Preparation of catalyst>
A coprecipitation method in which a basic solution is added to a solution containing a salt of copper or zinc (and optionally at least one of zirconium, aluminum or gallium) to precipitate these salts is preferably employed. In addition, among salts of copper and zinc (and optionally at least one of zirconium, aluminum and gallium), a basic solution is first added to a solution containing one or two components to precipitate one or two components, A sequential precipitation method in which the remaining components are added in a liquid containing the precipitate and precipitation is similarly performed is also suitably employed.

After washing the precipitate, the precipitate is dried in air at 300-300.
It is fired at a temperature of about 500 ° C. to be in an oxide state.
A predetermined amount of graphite is added to the fired product and mixed with a kneader or the like. If graphite is added and mixed and wetted with a solvent such as alcohol, it can be mixed more uniformly.

The obtained mixture is molded into a catalyst by a known method. The particle size and shape of the catalyst depends on the reaction method,
It can be arbitrarily selected depending on the shape of the reactor. This catalyst
Prior to use, it is reduced with a reducing gas such as H ₂ and CuO
Is converted to Cu for use.

<Synthesis of Liquid Phase Methanol> Using the above catalyst in the form of a fixed bed or a suspension bed, a raw material gas comprising hydrogen and carbon oxide is reacted in the presence of a solvent to synthesize methanol. You.

As the carbon oxide, a single gas of carbon dioxide or a mixed gas of carbon dioxide and carbon monoxide is used. As the solvent, a water-insoluble or hardly water-soluble solvent such as a hydrocarbon solvent is suitably used.

This liquid phase methanol synthesis reaction is typically carried out at a reaction temperature of 150 to 300 ° C. and a reaction pressure of 50 to 200.
Performed at atmospheric pressure.

<Action> When methanol is synthesized from a mixed gas containing carbon dioxide and hydrogen, unlike the reaction (b) below in which methanol is synthesized from synthesis gas (carbon monoxide and hydrogen), the following (a) As shown in the reaction formula of (2), water is produced in an equimolar amount with methanol. (B) CO ₂ + 3 H ₂ = CH ₃ OH + H ₂ O (b) CO + 2 H ₂ = CH ₃ OH

Therefore, when synthesizing methanol from a mixed gas of hydrogen and carbon oxides containing carbon dioxide, the deterioration of the catalyst proceeds under the influence of the generated water, and a stable methanol production rate is maintained. Difficult to do. Especially,
In the case of methanol synthesis by the liquid phase method, since a water-insoluble or poorly water-soluble solvent is often used, the generated water is likely to be adsorbed by a hydrophilic catalyst, which is considered to be a major factor causing deterioration. Can be

The inventors of the present invention have studied various methods for preventing the catalyst from deteriorating due to water, and as a result of intensive research based on the idea of adding and mixing graphite, which is relatively hard to wet with water, to the catalyst. It has been found that by including a specific amount of graphite having a low ash content in the catalyst, a stable methanol production rate can be maintained without lowering the methanol productivity.

A substance that imparts hydrophobicity to the catalyst is, for example, polytetrafluoroethylene, which is far more effective than graphite in terms of hydrophobicity. However, polytetrafluoroethylene is not suitable for long-term use at a high temperature such as 250 ° C. to 300 ° C. for performing a methanol reaction.

Usually, an industrial catalyst is used after being molded into a cylindrical shape or the like. At this time, about several percent of graphite is used as a molding aid. However, graphite is used only for ease of molding. It is not used from the viewpoint of catalyst deterioration or activity stability, and the amount of graphite at that time is not enough to ensure the hydrophobicity of the catalyst.

[0032]

The present invention will be described in more detail with reference to the following examples. Hereinafter, “parts” and “%” are expressed on a weight basis.

Example 1 Cu / ZnO / Zr prepared by a coprecipitation method according to a conventional method
25 parts of graphite having an ash content of 0.05% was added to 75 parts of an O ₂ / Al ₂ O ₃ (40/30/25/5 by weight) catalyst, mixed and molded to prepare a 1 to 2 mm catalyst.

This catalyst was reduced with a mixed gas of hydrogen and helium, and the size of Cu crystallites in the catalyst was measured by an X-ray diffractometer. The result was 7.0 nm, indicating that Cu active in methanol synthesis was highly dispersed. I knew it was there.

In order to confirm the effect of adding graphite, it was measured whether or not the crystal growth of Cu was suppressed by subjecting the above catalyst to a heat treatment in a system to which water and methanol were added. That is, 0.5 g of the graphite-added catalyst was placed in an autoclave having an internal volume of 110 ml, and 50 ml of dodecane, 2.25 g of water and 4.0 g of methanol were added to the autoclave as a solvent and heated at 250 ° C. for 50 hours. Was 22.0 nm. Although the crystallite size of Cu was large, it was found that the crystal growth of Cu was suppressed as compared with the catalyst shown in Comparative Example 1 described later.

Then, an activity test was carried out to evaluate the stability of the activity. That is, the opening of 3 ml of graphite-added catalyst is
Packed in a basket composed of 0.5mm wire mesh,
This was attached to a stirring shaft of an autoclave having an inner volume of 220 ml, and was allowed to rotate. 170 ml of dodecane as a reaction solvent was added to this autoclave, and H ₂ / CO ₂ was added.
= 75/25, and the reaction gas was supplied to the autoclave at a reaction pressure of 15 MPa and a reaction temperature of 250.
The reaction was carried out at a temperature of 500 ° C. and a stirring speed of 500 rpm. The reaction solution was continuously withdrawn at a rate of 5.0 ml / min from the bottom of the autoclave, introduced into the liquid-liquid separation tank, the reaction solvent was continuously drawn from the top of the liquid-liquid separation tank, and returned to the autoclave. On the other hand, the aqueous methanol solution that had been phase-separated in the liquid-liquid separation tank was extracted from the lower part of the liquid-liquid separation tank, returned to normal pressure, and the amounts of water and methanol produced were quantified. In the above reaction, the raw material gas consumed as the reaction proceeded was continuously injected into the autoclave through a pressure regulating valve so as to maintain a constant pressure.

As a result of the reaction, the methanol production rate at the beginning of the reaction was 504 (g-MeOH / L-Cat · hr), and the methanol production rate after 200 hours was 499 (g-MeOH / L-Cat · hr). The methanol production rate was stable with little change. Further, the methanol production rate after reacting for about 200 hours was higher than that of Comparative Example 1 described later.

FIG. 1 shows the relationship between the methanol production rate and the reaction time in Example 1. FIG. 1 also shows the results of Example 2 and Comparative Example 1 described below.

Example 2 Cu / ZnO / ZrO ₂ / Al ₂ O prepared by the coprecipitation method
₃ (40/30/25/5 by weight) To 85 parts of the catalyst, 15 parts of graphite having an ash content of 0.05% was added, mixed, molded, and then
mm of catalyst was prepared.

This catalyst was reduced with a mixed gas of hydrogen and helium, and the Cu crystallite size in the catalyst was measured by an X-ray diffractometer to find that it was 7.0 nm. As a result of heat treatment in the presence of water-methanol in the same manner as in Example 1, C
The crystallite size of u was 22.9 nm. Although the crystallite size of Cu was large as in Example 1, it was found that Cu crystal growth was suppressed as compared with the catalyst shown in Comparative Example 1 described later.

Therefore, an activity test was carried out in the same manner as in Example 1 to evaluate the stability of the activity. As a result, the methanol generation rate at the beginning of the reaction was 495 (g-MeOH / L-Cat.hr)
To 465 (g-MeOH / L-Cat.hr), but hardly decreased thereafter, and the methanol production rate after about 200 hours was 455 (g-MeOH / L-Cat.hr). The formation rate was stable with little change. FIG.
The relationship between the methanol production rate and the reaction time in Example 2 is shown below.

Comparative Example 1 Cu / ZnO / ZrO ₂ / Al ₂ O prepared by the coprecipitation method
₃ (40/30/25/5 by weight ratio)
A ~ 2 mm catalyst was prepared.

As a result of heat treatment in the same manner as in Example 1 in the presence of water-methanol, the crystallite size of Cu was 26.1 nm.
Met. The crystallite size of Cu was larger than in Example 1.

An activity test was carried out in the same manner as in Example 1. As a result, the methanol production rate at the beginning of the reaction was 530.
(g-MeOH / L-Cat.hr), the methanol production rate after about 200 hours was 410 (g-MeOH / L-Cat.hr), indicating that the methanol production rate was greatly reduced. FIG. 1 shows the relationship between the methanol production rate and the reaction time in Comparative Example 1.

Comparative Example 2 Cu / ZnO / ZrO ₂ / Al ₂ O prepared by the coprecipitation method
₃ (40/30/25/5 by weight ratio) 25 parts of graphite containing 12% of ash was added to 75 parts of the catalyst, mixed, and molded.
A 1-2 mm catalyst was prepared.

As a result of heat treatment in the presence of water-methanol in the same manner as in Example 1, the crystallite size of Cu was 24.0 nm.
The crystallite size of Cu was larger than that of Example 1 in which the same amount was added.

Comparative Example 3 Cu / ZnO / ZrO ₂ / Al ₂ O prepared by the coprecipitation method
₃ (40/30/25/5 by weight ratio) 35 parts of graphite having an ash content of 50 ppm were added to 65 parts of the catalyst, mixed, molded, and
A 2 mm catalyst was prepared.

As a result of heat treatment in the same manner as in Example 1 in the presence of water-methanol, the crystallite size of Cu was 20.6 nm.
The crystallite size of Cu was smaller than that of Example 1, and the effect of adding graphite was large. However, the methanol production rate was as low as 370 (g-MeOH / L-Cat.hr).

[0049]

The liquid-phase methanol synthesis catalyst of the present invention is specially designed so that a specific amount of graphite having a small ash content is contained in the catalyst. The methanol production rate can be maintained. Therefore, according to the present invention, liquid-phase methanol synthesis can be carried out industrially advantageously.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a methanol production rate and a reaction time in Examples 1 and 2 and Comparative Example 1.

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[Procedure amendment]

[Submission date] December 4, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of Invention] liquid phase meth no Le synthesis catalyst

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Daiki Watanabe 2-8-11 Nishi-Shimbashi, Minato-ku, Tokyo 7th Oriental Maritime Building 8th Floor Research Institute of Innovative Technology for the Global Environment (CO2) 72) Inventor Konosuke Hagiwara 2-8-11 Nishi-Shimbashi, Minato-ku, Tokyo 8th floor of the 7th Oriental Maritime Building Research Institute for Innovative Technology for the Earth, CO2 fixation project room (72) Inventor Masahiro Saito Ibaraki 16-3 Onogawa, Tsukuba City, National Institute of Advanced Industrial Science and Technology

Claims (4)

[Claims] 1. A catalyst for synthesizing methanol by reacting a raw material gas comprising hydrogen and carbon oxide in the presence of a solvent, the catalyst comprising a metal mainly composed of copper and zinc. And further contains graphite having an ash content of 1% by weight or less, and the content of the graphite in the entire catalyst is 10%.
Liquid-phase methanol synthesis catalyst, characterized in that the amount is from 30 to 30% by weight. 2. The liquid-phase methanol according to claim 1, wherein the catalyst further contains, in addition to copper, zinc and graphite, at least one metal component selected from the group consisting of aluminum, zirconium and gallium. Synthetic catalyst. 3. The liquid phase methanol synthesis catalyst according to claim 1, wherein the ash content in the graphite is 0.1% by weight or less. 4. The liquid phase methanol synthesis catalyst according to claim 1, wherein the solvent is a water-insoluble or poorly water-soluble solvent.